Alteration in cardiac uncoupling proteins and eNOS gene expression following high-intensity interval training in favor of increasing mechanical efficiency.

OBJECTIVES: High-intensity interval training (HIIT) increases energy expenditure and mechanical energy efficiency. Although both uncoupling proteins (UCPs) and endothelial nitric oxide synthase (eNOS) affect the mechanical efficiency and antioxidant capacity, their effects are inverse. The aim of this study was to determine whether the alterations of cardiac UCP2, UCP3, and eNOS mRNA expression following HIIT are in favor of increased mechanical efficiency or decreased oxidative stress. MATERIALS AND METHODS: Wistar rats were divided into five groups: control group (n=12), HIIT for an acute bout (AT1), short term HIIT for 3 and 5 sessions (ST3 and ST5), long-term training for 8 weeks (LT) (6 in each group). The rats of the training groups were made to run on a treadmill for 60 min in three stages: 6 min running for warm-up, 7 intervals of 7 min running on treadmill with a slope of 5° to 20° (4 min with an intensity of 80-110% VO2max and 3 min at 50-60% VO2max), and 5-min running for cool-down. The control group did not participate in any exercise program. Rats were sacrificed and the hearts were extracted to analyze the levels of UCP2, UCP3 and eNOS mRNA by RT-PCR. RESULTS: UCP3 expression was increased significantly following an acute training bout. Repeated HIIT for 8 weeks resulted in a significant decrease in UCPs mRNA and a significant increase in eNOS expression in cardiac muscle. CONCLUSION: This study indicates that Long term HIIT through decreasing UCPs mRNA and increasing eNOS mRNA expression may enhance energy efficiency and physical performance.

Cardioprotective Effect of High Intensity Interval Training and Nitric Oxide Metabolites (NO2 (-), NO3 (-)).

BACKGROUND: The aim of this study was to investigate the effects of High-Intensity Interval Training (HIIT) on nitric oxide metabolites (NO2(-), NO3(-)) and myocardial infarct size after Ischemia/Reperfusion (I/R) injury in healthy male rats. METHODS: A total of 44 Wistar rats were randomly divided into 4 groups including HIIT (n=8), HIIT + IR protocol (n=14), control (n=8), and control + IR (n=14). Each training session of HIIT consisted of 1 hour of exercise in three stages: 6-minute running at 50-60% VO2max for warm-up; 7 intervals of 7-minute running on treadmill with a slope of 5° to 20° (4 minutes with an intensity of 80-100% VO2max and 3 minutes at 50-60% VO2max); and 5-minute running at 50-60% VO2max for cool-down. The control group did not participate in any exercise program. Nitric Oxide (NO) and its metabolites were measured by using Griess reaction test. RESULTS: The results showed that eight weeks of exercise training exerted a significantly increasing effect on nitrite (8.55 µmol per liter, equivalent to 34.79%), nitrate (62.02 µmol per liter, equivalent to 149.48%), and NOx (66 µmol per liter, equivalent to 98.11%) in the HIIT group compared with the control group. The results showed myocardial infract size (IS) was significantly smaller (23.2%, P<0.001) in the exercise training group compared with the control group. CONCLUSION: Incremental changes in NO-NO3 (-), NO2 (-) axis are one of mechanisms through which HIIT program can protect the heart from I/R injury and decrease myocardial infarction.

The effect of high intensity interval training on cardioprotection against ischemia-reperfusion injury in wistar rats.

The aims of the present study were to determine whether short term high intensity interval training (HIIT) could protect the heart against ischemia reperfusion (IR) injury; and if so, to evaluate how long the exercise-associated protection can be lasted. Sixty-three rats were randomly assigned into sedentary (n = 15), sham (n = 7), and exercise groups (n = 41). Rats in the exercise groups performed 5 consecutive days of HIIT on treadmill: 5 min warm up with 50 % VO2max, 6×2 min with 95-105 % VO2max (about 40 to 45 m/min), 5×2 min recovery with 65-75 % VO2max (about 28 to 32 m/min), and 3 min cool down with 50 % VO2max, all at 0 % grade. Animals exposed to an in vivo cardiac IR surgery, performed at days 1, 7, and 14 following the final exercise session. Ischemia-induced arrhythmias, myocardial infarct size (IS), plasma lactate dehydrogenase (LDH) and creatine kinase (CK) activities were measured in all animals. Compared to sedentary rats, exercised animals sustained less IR injury as evidenced by a lower size of infarction and lower levels of LDH and CK at day one and day 7 post exercise. In comparison of sedentary group, IS significantly decreased in EX-IR1 and EX-IR7 groups (50 and 35 %, respectively), but not in EX-IR14 group (19 %). The exercise-induced cardioprotection disappeared 14 days following exercise cessation. There were no significant changes in ischemia-induced arrhythmia between exercised and sedentary rats. The results clearly demonstrate that HIIT protects the heart against myocardial IR injury. This protective effect can be sustained for at least one week following the cessation of the training.

Protective effect of crocin against reperfusion-induced cardiac arrhythmias in anaesthetized rats.

The aim of the present study was to investigate the effects of crocin - a natural antioxidant derived from saffron - on cardiac reperfusion-induced arrhythmia and antioxidant systems such as catalase and superoxide dismutase (SOD) enzyme activities, glutathione (GSH) and malondialdehyde (MDA, as a marker of lipid peroxidation) levels. Rats in 4 experimental groups were administered crocin (20 mg/kg/day) or vehicle (i.p.) for 21 days with or without cardiac ischemia-reperfusion (IR). At the end of this period, hearts of anaesthetized animals in IR and "Cr + IR" groups were subjected to 10 min occlusion of the left anterior descending coronary artery and thereafter reperfused for 30 min. The results suggest that crocin is partially capable of suppressing reperfusion-induced arrhythmias. Compared to control group, ischemic-reperfusion injury significantly decreased SOD activity and GSH level and increased MDA level of heart muscle. "Cr + IR" group showed remarkably increased catalase activity in heart tissue (28.7 ± 6.6 vs. 23.6 ± 4.1 U/mg protein, P < 0.05) compared to the IR group. The level of cardiac tissue SOD activity in the "Cr + IR" group animals did not decline significantly compared to rats that were administered crocin alone with no ischemia. The results suggest a protective role of crocin on cardiac reperfusion arrhythmias which may at least partially be related to stability or even amplification of antioxidant systems. Crocin may potentially be useful for treatment or prevention of arrhythmias in patients with ischemic heart disease and this issue remains to be investigated in future clinical studies.

Influence of ramiprilat and losartan on ischemia reperfusion injury in rat hearts.

UNLABELLED: HYPOTHESIS/INTRODUCTION: Our aim was to investigate whether a non-hypotensive dose of ramiprilat and losartan has myocardial protective effects during myocardial ischemia/reperfusion in vivo. MATERIALS AND METHODS: Three groups of rats were given 10 mg/kg per day of losartan for one (L-1W), four (L-4W) or 10 (L-10W) weeks. Another three groups were given 50 µg/kg per day of ramiprilat for one (R-1W), four (R-4W) or 10 (R-10W) weeks. The animals underwent 30 min of left anterior descending artery occlusion and subsequent reperfusion for 120 min. RESULTS: Myocardial infarct size (IS) was reduced in R-1W (28.4 ± 6.3%, p < 0.001), R-4W (27.8 ± 7.4, p < 0.001), L-4W (31.8 ± 6%, p < 0.05) and L-10W (25.3 ± 5.7, p < 0.001) groups compared with a saline group (48.3 ± 7.8%). A significant reduction in the number of ventricular ectopic beats (VEBs) was noted in groups R-1W (209 ± 41, p < 0.01), R-4W (176 ± 39, p < 0.01), L-4W (215 ± 52, p < 0.05) and L-10W (191 ± 61, p < 0.01 vs. saline 329 ± 48). The incidence of irreversible ventricular fibrillation (VF) and mortality were decreased significantly only in L-10W group. There were no significant decreases in episodes of VT, the incidence of irreversible VF and mortality in all of the groups treated with ramiprilat. CONCLUSION: These data indicate that losartan and ramiprilat protect the heart against ischemia/reperfusion injury independently of their hemodynamic effects but in a time-dependent manner.

Pretreatment with hyperoxia reduces in vivo infarct size and cell death by apoptosis with an early and delayed phase of protection.

OBJECTIVE: Exposure to normobaric hyperoxia protects the heart against ischemia-reperfusion injury ex vivo. In the present study, we investigated the effect of the early and late phase of hyperoxia on in vivo myocardial infarction and apoptosis. METHODS: Rats were exposed to room air preoxygenation (O(2)≥ 95%) followed by regional ischemia (30 min) and 0, 90, 180, and 360 min of reperfusion. Hyperoxic exposure was performed for 120 min either immediately or 24h before coronary occlusion followed by 360-min reperfusion. Infarct size was evaluated by Evans blue/triphenyltetrazolium chloride staining. Apoptosis in the infarcted area was evaluated by terminal deoxy-nucleotidyl transferase-mediated deoxy uridine triphosphate (dUTP) nick end-labeling (TUNEL). Caspase 3 activity was measured by fluorometric enzyme assay, Bcl-2 and Bax protein expression assessed by western blotting and DNA laddering assessed with DNA gel electrophoresis. RESULTS: The infarct size did not increase with increasing duration of reperfusion. However, apoptosis as evaluated by Bcl-2/Bax ratio, caspase 3 activity, and TUNEL-positive cells increased with increasing time of reperfusion. Both early and delayed pretreatment with hyperoxia reduced infarct size (p = 0.0013, p = 0.046), ameliorated ischemic arrhythmias and increased Bcl-2/Bax ratio (p = 0.015, p = 0.0159). Only hyperoxia immediately before coronary occlusion decreased caspase 3 activity (p = 0.026) and decreased TUNEL-positive staining (p = 0.046) with no visible DNA laddering. CONCLUSIONS: Detection of myocardial apoptosis increased with prolongation of reperfusion time, as opposed to infarct detection where reperfusion was essential to detect infarction, but the infarct size did not increase with time. Pretreatment with hyperoxia significantly decreased infarct size and apoptotic cell death. Pretreatment, immediately before coronary occlusion, was most cardioprotective.

Dietary virgin olive oil reduces blood brain barrier permeability, brain edema, and brain injury in rats subjected to ischemia-reperfusion.

Recent studies suggest that dietary virgin olive oil (VOO) reduces hypoxia-reoxygenation injury in rat brain slices. We sought to extend these observations in an in vivo study of rat cerebral ischemia-reperfusion injury. Four groups, each consisting of 18 Wistar rats, were studied. One group (control) received saline, while three treatment groups received oral VOO (0.25, 0.5, and 0.75 mL/kg/day, respectively). After 30 days, blood lipid profiles were determined, before a 60-min period of middle cerebral artery occlusion (MCAO). After 24-h reperfusion, neurological deficit scores, infarct volume, brain edema, and blood brain barrier permeability were each assessed in subgroups of six animals drawn from each main group. VOO reduced the LDL/HDL ratio in doses of 0.25, 0.5, and 0.75 mL/kg/day in comparison to the control group (p < 0.05), and offered cerebroprotection from ischemia-reperfusion. For controls vs. doses of 0.25 vs. 0.5 vs. 0.75 mL/kg/day, attenuated corrected infarct volumes were 207.82 +/- 34.29 vs. 206.41 +/- 26.23 vs. 124.21 +/- 14.73 vs. 108.46 +/- 31.63 mm3; brain water content of the infarcted hemisphere was 82 +/- 0.25 vs. 81.5 +/- 0.56 vs. 80.5 +/- 0.22 vs. 80.5 +/- 0.34%; and blood brain barrier permeability of the infarcted hemisphere was 11.31 +/- 2.67 vs. 9.21 +/- 2.28 vs. 5.83 +/- 1.6 vs. 4.43 +/- 0.93 micro-g/g tissue (p < 0.05 for measures in doses 0.5 and 0.75 mL/kg/day vs. controls). Oral administration of VOO reduces infarct volume, brain edema, blood brain barrier permeability, and improves neurologic deficit scores after transient MCAO in rats.

Pretreatment with oxygen protects rat kidney from cisplatin nephrotoxicity.

Cisplatin (CP) nephrotoxicity is mainly due to reactive oxygen species. Oxygen pre-exposure as a mild oxidative stress may enhance some endogenous defense mechanisms, so its effect on cisplatin-induced acute renal failure was investigated in present study. Twenty-four rats were divided into four groups. The O(2)+ CP and Air + CP groups were were subjected to i.p. injection of 5 mg/kg cisplatin, and in the Air + Saline and O(2) + Saline groups, saline was injected instead of cisplatin. O(2)+ CP and O(2)+ Saline groups were pretreated with oxygen (3h/d for two days), and the other two groups were pretreated with room air. Cisplatin was administered 24 h after last pretreatment session. Three days after cisplatin injection, plasma samples were obtained, and parts of kidney tissue were frozen for biochemical analysis or fixed in formalin for histological assessments. Preconditioning with oxygen prior to cisplatin administration led to reduced tubular necrosis and luminal cast formation and improvement of renal function, as was evidenced by significant reduction in plasma creatinine and urea levels. Oxygen pretreatment also significantly reversed cisplatin-induced reduction in renal catalase activity and glutathione level. It could be concluded that oxygen pretreatment could have a delayed protective effect against cisplatin nephrotoxicity, and that increased renal catalase activity may be involved in this protective effect of hyperoxia.

Delayed cardioprotective effects of hyperoxia preconditioning prolonged by intermittent exposure.

BACKGROUND: In our previous study, it was indicated that pre-exposing rats to normobaric hyperoxia could induce a late preconditioning against infarction and arrhythmia. In this study, attempts were made to know whether the intermittent pre-exposure to the same environment could prolong the late phase of hyperoxia preconditioning. METHODS: In the first series of experiments, rats were divided into five groups; group 1 was pre-exposed to normal air (NOR) and the other groups to hyperoxic air (O(2)>95%, 120 min once a d) 12, 24, 48, and 72 h (H12, H24, H48, and H72 groups) before 30 min ischemia. In the second series of experiments, rats were pre-exposed to intermittent hyperoxic air (1, 2, or 3 consecutive d) at different times before being subjected to ischemia (H48, H2-48, H2-72, H3-72, and H3-96 groups). The infarct size was measured by triphenyltetrazolium chloride staining, and lead II of electrocardiogram recorded to monitor ischemic-induced arrhythmia. RESULTS: Compared with NOR group, the infarct size and incidence of arrhythmia were reduced significantly in H24 and H48 groups. When the exposure periods were enhanced to 2 d, the infarct size did not decrease significantly, but the incidence of arrhythmia reduced. When the pre-exposure times were enhanced to 3 d, both the infarct size and incidence of arrhythmia decreased significantly in H3-72 group, but not in H3-96 group. CONCLUSION: These results show that the late phase of hyperoxia preconditioning may last for more than 48 h and prolong by intermittent per-exposure to the same environment.

Hyperoxia-induced protection against rat's renal ischemic damage: relation to oxygen exposure time.

BACKGROUND: Pre-exposure to hyperoxic gas (>or= 95%) has been shown to protect the heart and central nervous system from ischemia-reperfusion injury. In the present study, we investigated whether oxygen pretreatment induces delayed renal protection in rats. The possible role of some renal antioxidant agents was also investigated. MATERIALS AND METHODS: Adult male Wistar rats were kept in a hyperoxic (HO) (>or= 95% O(2)) environment for 0.5 h, 1 h, 2 h, 3 h, 6 h, and 2 h/day for three consecutive days and 4 h/day for six consecutive days, and control group (IR) animals were kept in the cage with no HO, one day before subjecting their kidney to 40 minutes of ischemia and 24h of reperfusion. Renal function was assessed by comparing plasma creatinine (Cr), blood urea nitrogen (BUN), creatinine clearance (CLCr), and fractional excretion of sodium (FENa%). Histopathological injury score was also determined according to the Jablonski method. To examine the antioxidant system induction by hyperoxia, we measured renal catalase and superoxide dismutase activity, and renal glutathione and malondialdehyde content. RESULTS: Our data demonstrated that only in 4 h/day HO for six consecutive days, the renal function tests (Cr, CLCr, BUN, and FENa%) and Jablonski histological injury were better than control group (p < 0.05). The beneficial effect of oxygen pretreatment in this group was associated with increased renal catalase activity compared with those obtained from control group (p < 0.05). CONCLUSION: The present study demonstrates that repeated exposure to hyperoxic (>or= 95% O(2)) environment can reduce subsequent rat's renal ischemia-reperfusion damage. Induction of endogenous antioxidant system may partially explain this beneficial effect of hyperoxic preconditioning.

Preconditioning with sublethal ischemia or intermittent normobaric hyperoxia up-regulates glutamate transporters and tumor necrosis factor-alpha converting enzyme in the rat brain.

INTRODUCTION: Recent studies suggest that sublethal ischemia and intermittent normobaric hyperoxia (InHO) protect the brain from subsequent ischemic injury. In this, changes in the expression of excitatory amino-acid transporters (EAATs) and tumor necrosis factor-alpha converting enzyme (TACE) may play a role. We sought to identify and clarify the nature of any such changes. METHOD: Rats were divided into 3 experimental groups, each of 15 animals. The first group was exposed to normobaric hyperoxia (fractional inspired oxygen concentration 95%) for 4 hours/day for 6 consecutive days (InHO). The second group acted as controls, and was exposed to 21% oxygen in the same chamber (room air). The third group acted as a model of ischemic preconditioning, and was exposed to 21% oxygen in the same chamber and subjected to 10 minutes of temporary middle cerebral artery (MCA) occlusion (tMCAO). After 24 hours, 9 animals from each group were subjected to 60 minutes of right MCA occlusion (MCAO). After 24 hours of reperfusion, neurologic deficit score and infarct volume were assessed in MCAO-operated subgroups. The remaining 6 animals in each group remained intact and, 48 hours after pretreatment, were killed for assessment of EAATs and TACE expression in the ipsilateral hemisphere. RESULTS: Preconditioning with InHO and tMCAO decreased neurologic deficit score and infarct volume, and increased expression of EAAT1, EAAT2, EAAT3, and TACE. CONCLUSION: InHO and tMCAO are associated with expression of EAAT1, EAAT2, EAAT3, and TACE, consistent with an active role in the genesis of ischemic protection.

Ischemia and reperfusion-induced arrhythmias: role of hyperoxic preconditioning.

BACKGROUND: Hyperoxic preconditioning is known to protect the heart against necrosis and contractile dysfunction, but protection against arrhythmias has not been well characterized. OBJECTIVE: The authors hypothesized that pre-exposure to normobaric hyperoxia (H) reduces ischemia and reperfusion-induced arrhythmias in isolated rat hearts. METHODS: Following 60 and 180 min of hyperoxia treatment, rat hearts were isolated immediately (H60 and H180) or 24 h afterward (H60/24 and H180/24), and subjected to 30 min of regional ischemia followed by 120 min of reperfusion. Occurrence, number, and duration of arrhythmias were analyzed during ischemia and reperfusion. In addition, cardiac infarct size was also assessed. RESULTS: Sixty and 180 min of breathing hyperoxic gas induced significant protection against severe ischemia and reperfusion-induced arrhythmias. Total number of premature ventricular beats was markedly attenuated by hyperoxia pre-exposure, especially in H60 and H180 groups. Duration of ventricular tachycardia and ventricular fibrillation was also affected by hyperoxia. Hyperoxia reduced the number of ventricular tachycardia episodes in ischemia and reperfusion phase. Accordingly, severity of arrhythmias (arrhythmia score) and infarct size were lower in hyperoxia-treated groups. The effects were more pronounced using hyperoxia immediately before harvesting the heart. CONCLUSION: These results indicate that hyperoxic preconditioning attenuates ventricular ischemia and reperfusion-induced arrhythmias in isolated rat hearts, decreases cardiac infarct size, and improves postischemic heart function. The effects seem to depend on the time course after hyperoxia treatment.

In vitro assessment of paraoxon effects on GABA uptake in rat hippocampal synaptosomes.

Treating organophosphate poisoning is achieved mainly using compounds with anticholinergic characteristics. Nevertheless currently the focus of attention is aimed at examining their interference with other neurotransmitter systems. The present investigation studied the potential interactions between paraoxon and GABA uptake in hippocampal synaptosomes. Wistar rats weighing 200-250 g were used. Hippocampal synaptosomes were prepared and incubated with [(3)H] GABA in the presence of different doses of paraoxon for 10 min at 37 degrees C; and were then layered in chambers of a superfusion system and the [(3)H] GABA uptake was measured. Our finding revealed that mean GABA uptake decreased by 21%, 42%, 37%, 20%, and 8% of the corresponding control values in the presence of paraoxon concentrations of 0.01, 0.1, 1, 10, and 100 microM, respectively which was significant at 0.1 and 1 microM of paraoxon (P<0.05). In conclusion, micromolar concentrations of paraoxon were shown to interfere with GABA uptake in hippocampal synaptosomes, which indicates the GABA transporters may play a role in organophosphate-induced convulsions.

Delayed protective effects of hyperoxia against cardiac arrhythmias and infarction in anesthetized rats.

BACKGROUND: Previous studies have shown that pretreatment with normobaric hyperoxia has cardioprotective effect in isolated rat heart. The present study was designed to test the hypothesis that pretreatment normobaric hyperoxia could induce delayed cardioprotection effect in an in vivo regional heart ischemia. MATERIALS AND METHODS: Experiment 1: Rats were exposed to normobaric normoxia or to normobaric hyperoxia (O(2) > 95%) for 15, 30, 60, 120, and 180 min (H15, H30, H60, H120, and H180 groups, respectively). After 24 h, they were subjected to 30 min regional ischemia and 90 min reperfusion. Then, the hearts were harvested for measurement of infarct size. Lead II of electrocardiogram was continuously recorded for analysis of ischemic arrhythmias. Experiment 2: Different oxygen concentrations were tested in the same model of heart ischemia. RESULTS: Compared with normoxia group, infarct size significantly reduced in H120 and H180 groups (from 48.1 +/- 4 to 31.4 +/- 3.3 and 30 +/- 2.4, respectively); 120 and 180 min of >95% hyperoxia significantly reduced the number of ventricular beats (from 314 +/- 34.9 to 173 +/- 20.3 and 178 +/- 15.7, respectively) and incidence of ventricular fibrillation (from 66.8% to 30% and 22.2%, respectively). When the oxygen concentration decreased to 80%, its effect on infarct size was abolished; however, its antiarrhythmic effect persisted. Further reduction of oxygen concentration eliminated both the effects. CONCLUSION: These results show that hyperoxia pretreatment may induce delayed anti-infarct and antiarrhythmic effects in anesthetized rats. These effects are dependent on the exposure time and oxygen concentration.

Normobaric hyperoxia induces ischemic tolerance and upregulation of glutamate transporters in the rat brain and serum TNF-alpha level.

Recent studies suggest that intermittent and prolonged normobaric hyperoxia (HO) results in ischemic tolerance to reduce ischemic brain injury. In this research, we attempted to see changes in excitatory amino acid transporters (EAATs) and TNF-alpha levels following prolonged and intermittent hyperoxia preconditioning. Rats were divided into four experimental groups, each of 21 animals. The first two were exposed to 95% inspired HO for 4 h/day for 6 consecutive days (intermittent HO, InHO) or for 24 continuous hours (prolonged HO, PrHO). The second two groups acted as controls, and were exposed to 21% oxygen in the same chamber. Each main group was subdivided to middle cerebral artery occlusion (MCAO-operated), sham-operated (without MCAO), and intact (without any surgery) subgroups. After 24 h from pretreatment, MCAO-operated subgroups were subjected to 60 min of right MCAO. After 24 h reperfusion, neurologic deficit score (NDS) and infarct volume were measured in MCAO-operated subgroups. EAATs expression and serum TNF-alpha levels were assessed in sham-operated and intact subgroups. Preconditioning with prolonged and intermittent HO decreased NDS and upregulated EAAT1, EAAT2, and EAAT3 and increased serum TNF-alpha levels significantly. Although further studies are needed to clarify the mechanisms of ischemic tolerance, the intermittent and prolonged HO seems to partly exert their effects via increase serum TNF-alpha levels and upregulation of EAATs.

Synaptosomal GABA uptake decreases in paraoxon-treated rat brain.

A synaptosomal model was used to evaluate in vivo effects of paraoxon on the uptake of [(3)H]GABA in rat cerebral cortex and hippocampus. Male Wistar rats were given a single intraperitoneal injection of one of three doses of paraoxon (0.1, 0.3, or 0.7 mg/kg) and acetylcholinesterase (AChE) activity in the plasma, cerebral cortex, and hippocampus was measured at 30 min, 4h, and 18 h after exposure. [(3)H]GABA uptake in synaptosomes was also studied in another series of animals. Paraoxon administration (0.3 and 0.7 mg/kg) caused significant inhibition of AChE activity in the plasma and both brain areas at all time points. 0.1 mg/kg paraoxon significantly inhibited AChE activity but only in the plasma for 4h, the activity was completely recovered at 18 h. GABA uptake was significantly (p<0.001) reduced in both cerebral cortex (18-32%) and hippocampal (16-23%) synaptosomes at all three time points after administering 0.7 mg/kg of paraoxon, a dose that seems to be sufficient to induce seizure activity. L-DABA, an inhibitor of neuronal GABA transporter, allowed us to conclude that the uptake was mediated primarily by neuronal GABA transporter GAT-1. In conclusion, present data suggests that GABA uptake by synaptosomes decreases probably secondary to paraoxon-induced seizure activity.

Preconditioning with oxygen attenuates rat renal ischemia-reperfusion injury.

BACKGROUND: Short time pretreatment with oxygen is reported to be protective against subsequent ischemia-reperfusion (IR) injury of heart and spinal cord in some animal models. The purpose of this study was to investigate the effects of pre-exposure to hyperoxic environment on rat renal IR injury for the first time. MATERIALS AND METHODS: The effects of 1 h/d pretreatment with oxygen (>or=95%) for 5 days on a right nephrectomized rat model of renal IR injury was investigated by comparing creatinine clearance, fractional excretion of sodium, plasma creatinine, blood urea nitrogen, and histological injury scores among three groups: IR (40 min ischemia-24 h reperfusion), sham (no IR), and hyperoxia (5 days intermittent pretreatment with oxygen + IR). RESULTS: Intermittent pretreatment with oxygen resulted in significant improvement of creatine clearance and fractional excretion of sodium (P

Effects of chronic exercise on endothelial dysfunction and insulin signaling of cutaneous microvascular in streptozotocin-induced diabetic rats.

BACKGROUND: Abnormalities of the modulatory roles played by the endothelium and/or smooth muscle may be critical and initiating factors in the development of diabetic vascular disease. Decreased phosphatidylinositol 3-kinase (PI3-K)/Akt pathway activity and impaired nitric oxide production through this pathway may play pivotal roles in the diabetes-induced vascular dysfunction. Several findings have demonstrated that exercise training has therapeutic and protective effects in type 1 diabetes and could correct endothelial dysfunction. The molecular mechanisms, however, are only partially understood. METHOD: Male Wistar rats (220+/-10 g, N=60) were made diabetic by streptozotocin (60 mg/kg, subcutaneously). After 1 week of diabetes induction, animals were submitted to exercise training for 10 weeks on a treadmill. To characterize cutaneous microvascular responses by laser Doppler flowmetery, animals were deeply anesthetized by intraperitoneal injection of pentobarbital sodium (60 mg/kg) and placed on a heating pad. A rectal thermometer was inserted and body temperature was maintained at 37+/-0.5 degrees C. A tracheotomy was performed to minimize respiratory difficulties. Systemic arterial blood pressure and heart rate were measured by using a tail-cuff during assessment of cutaneous blood flow. RESULTS: (i) Acetylcholine-induced cutaneous perfusion were increased significantly by training in the diabetic groups; (ii) Cutaneous microvascular responses to sodium nitroprusside did not alter in control and diabetic animals by training; and (iii) Local microinjection of insulin increased cutaneous blood flow in trained diabetic and trained control rats compared with age-matched sedentary diabetic and sedentary control normal rats. The administration of wortmannin (PI3K inhibitor) and N-nitro-L-arginine ( nitric oxide synthase inhibitor) before insulin, however, attenuated the increase in cutaneous blood flow in trained diabetic and normal rats. CONCLUSIONS: Chronic exercise improved endothelium-dependent dilatation and potentiated insulin vascular function, possibly by PI3-kinase pathway in diabetic rats.

The effect of paraoxon on GABA uptake in rat cerebellar synaptosomes.

BACKGROUND: The compounds used to treat organophosphate (OP) poisoning are not able to fully alleviate long-lasting effects. They are mainly used to antagonize the cholinergic effects of OPs; however, non-cholinergic effects such as interference with different neurotransmitter systems, especially GABA release and uptake, are now attracting more attention. MATERIAL/METHODS: Cerebellar synaptosomes were used to investigate any potential interaction between paraoxon and GABA uptake. The cerebella of 250- to 280-g Wistar rats were rapidly dissected out, homogenized, centrifuged, and incubated with 0.004 microM [(3)H]GABA in the presence of different doses of paraoxon for 15 minutes at 37 degrees C. At the end of the incubation period, the synaptosomes were layered in chambers of a superfusion system (UGO). To assay the amount of [(3)H]GABA uptake, radioactivity was measured using a beta-counter (Winspectrul). RESULTS: Mean GABA uptake was 111, 95, 71, 73, and 75 percent of the control values in the presence of paraoxon concentrations of 0.01, 0.1, 1, 10, and 100 microM, respectively. Accordingly, GABA uptake was significantly reduced at doses 1, 10, and 100 microM of paraoxon (P<0.05). CONCLUSIONS: Paraoxon may interfere with GABA uptake by cerebellar synaptosomes at micromolar concentrations or higher.

Paraoxon inhibits GABA uptake in brain synaptosomes.

To investigate possible effect of paraoxon (10(-9)-10(-3)M) on GABA uptake, we used rat cerebral cortex synaptosomes. K(m) and V(max) of GABA uptake were determined in presence of paraoxon (10(-3)M). Acetylcholine and its antagonists (atropine and mecamylamine) were used for evaluating cholinergic-dependency of uptake. Type of transporter involved was determined by using glial (beta-alanine) and neuronal (DABA) GABA uptake inhibitors. The results of the study showed that paraoxon at low doses (10(-9)-10(-6)M) increased and at high doses (10(-5)-10(-3)M) decreased GABA uptake. One millimolar paraoxon significantly decreased V(max) (175.2+/-4.23 vs. 80.4+/-2.03, P<0.001) of GABA uptake while had no effect on its K(m). DABA significantly decreased GABA uptake (P<0.001) while beta-alanine had no effect. In conclusion, present data suggests that paraoxon probably acts as non-competitive antagonist of GABA uptake.